Intermittent Drive Systems

ABSTRACT

To fold sheets of newsprint ( 1 ), a ring gear  7  is driven in rotation by a motor  11  under the control of a controller  12  such that, for most of the time, the ring gear  7  rotates at the same speed as a folding cylinder  2  and arms  8 . When it is desired to initiate a folding operation, the ring gear  7  is momentarily stopped or slowed. The relative motion that occurs between the ring gear  7  and planet gears on the arms  8  causes the planet gears  9  to rotate about their axes and respective tucking blades  6  mounted on the planet gears  9  to protrude above the surface of the cylinder  2 , where they engage collated sheets on the cylinder surface and push them into the nip of folding rollers ( 4 ). Upon completion of the movement of the planet gears  9  and associated tucking blades  6 , the ring gear  7  is again caused to move at the same angular speed as the arms  8 , such that the tucking blades  6  retain their “silenced” positions below the surface of the cylinder  2.

The present invention relates to intermittent drive systems and isconcerned particularly, although not exclusively, with intermittentdrive systems for tucking blades that are used for cutting, collatingand folding sheets in, for example, the newspaper printing industry.

In a conventional newspaper printing press, a plurality of webs ofprinted paper are fed to a cutting and folding station, where they arecut and entrained in layers on a folding cylinder. As the foldingcylinder rotates, a tucking blade is caused to protrude from thecylinder at a predetermined angular position of the cylinder, where theblade engages the layers of printed paper on the surface of the cylinderand pushes them into the nip of a folding roller assembly, where thesheets of paper are folded and then passed on to subsequent stations forfurther possessing.

In such a conventional arrangement, the tucking blade is activated atthe same angular position, upon each revolution of the cylinder. Inpractice, a number of tucking blades may be provided at regularintervals around the folding cylinder, for faster operation.

Such a conventional arrangement is unsuitable for modern digitalprinting presses. One reason is that, with digital presses, the pagecontent is varied serially along the web of newsprint (paper), ratherthan combining a plurality of webs that are printed identically alongeach web and shifted in phase. In a digital arrangement, when the web iscut, successive sheets have to be collated on the folding cylinder,before they can be folded. In consequence, it is necessary to operatethe tucking blade only intermittently, rather than invariably upon eachrevolution of the folding cylinder.

There is thus a requirement for an intermittent drive mechanism tooperate a tucking blade on a folding cylinder, in a manner compatiblewith collation, cutting and folding of a printed web from a digitalprinting press. Moreover, it is desirable for such a mechanism to becapable of operating at the very high throughput speeds of which moderndigital printing presses are capable.

Typically, in a digital printing press, printing is effected by digitalmeans using a rotating drum onto which an electronic image is imposed byan electrostatic charge. This in turn attracts a toner powder, orliquid, which is deposited on the web of paper. Using an electrostaticdischarge device, the image on the drum is removed ready to receive afresh image, thereby giving sequential pagination as the web of paperpasses through the printing press. Drum diameter has no relationship tothe print length.

Preferred embodiments of the invention aim to provide an intermittentdrive mechanism that meet such requirements.

According to one aspect of the present invention, there is provided asheet handling system comprising:

-   -   a. a cylinder arranged to engage a sheet on the outer        circumferential surface of the cylinder and to transport the        sheet from an entry position to an exit position by rotation of        the cylinder about its axis; and    -   b. a drive mechanism mounted at least partly within the cylinder        and arranged to cause a member to protrude intermittently from        the surface of the cylinder to engage a sheet on that surface:    -   c. said drive mechanism comprising:        -   i. a primary gear mounted for rotation about an axis            parallel to the cylinder axis;        -   ii. an arm extending radially of the cylinder and mounted            for rotation about an axis parallel to the cylinder axis;            and        -   iii. a planet gear mounted for rotation on said arm, in            driving engagement with said primary gear, and operatively            connected to said member:

wherein:

-   -   d. said primary gear is arranged to rotate according to a first        velocity profile;    -   e. said arm is arranged to rotate according to a second velocity        profile; and    -   f. said first and second velocity profiles are such that:        -   i. said planet gear rotates to cause said member to protrude            from the surface of the cylinder at first selected times            when the cylinder is in a given angular position; and        -   ii. said planet gear does not rotate to cause said member to            protrude from the surface of the cylinder at second selected            times when the cylinder is in said given angular position.

Preferably, said primary gear is mounted for rotation about the cylinderaxis.

Preferably, said arm is mounted for rotation about the cylinder axis.

The said member may be a tucking blade that cooperates with a foldingnip to fold said sheet.

The said member may be a cutting blade.

The said member may be a numbering head.

Preferably, said primary gear is a sun gear.

Said primary gear may be a ring gear.

A sheet handling system as above may further comprise a motor arrangedto drive said primary gear in rotation.

A sheet handling system as above may further comprise a motor arrangedto drive said arm in rotation.

Preferably, said arm is fixed relative to the cylinder such that the armrotates with the cylinder.

Said primary gear may be fixed relative to the cylinder such that thearm rotates with the cylinder.

A sheet handling system as above may further comprise control meansarranged to determine said first and/or second velocity profile.

Preferably, said control means is arranged to control movement of atleast one electric motor arranged to drive said primary gear and/or armand/or cylinder in rotation.

Preferably, a sheet handling system as above further comprises retainingmeans arranged to retain one or more sheet on the cylinder.

Preferably, a sheet handling system as above further comprises meansarranged to engage and release said retaining means at times fixed inrelation to operation of said member.

Preferably, a sheet handling system as above further comprises cuttingmeans arranged to cut a web of material into sheets as it is fed ontothe cylinder.

Preferably, a sheet handling system as above comprises a plurality ofplanet gears mounted for rotation on respective arms of a planet carrierand in driving engagement with said primary gear:

A sheet handling system as above may comprise a plurality of membersarranged to protrude intermittently from the surface of the cylinder toengage a sheet on that surface.

Preferably, each said planet gear is operatively connected to arespective one of said members.

A sheet handling system as above may further comprise guide meansarranged to constrain movement of said planet gear when said cylinder isin said given angular position.

Preferably, said guide means is such as to constrain movement such thatsaid planet gear may occupy only two possible angular positions whensaid cylinder is in said given angular position.

In another aspect, the invention provides a printing press incorporatinga sheet handling system according to any of the preceding aspects of theinvention, arranged to cut and/or collate and/or fold printed sheets ofnewsprint.

Such a printing press may be arranged to feed a single web of printednewsprint onto the cylinder, where the web is cut, collated and folded.

Printing may be effected by a digital process.

In another aspect, the invention provides an intermittent drive systemcomprising:

-   -   a. a cylinder mounted for rotation about its axis; and    -   b. a drive mechanism mounted at least partly within the cylinder        and arranged to cause a member to protrude intermittently from        the surface of the cylinder:    -   c. said drive mechanism comprising:        -   i. a primary gear mounted for rotation about an axis            parallel to the cylinder axis;        -   ii. an arm extending radially of the cylinder and mounted            for rotation about an axis parallel to the cylinder axis;            and        -   iii. a planet gear mounted for rotation on said arm, in            driving engagement with said primary gear, and operatively            connected to said member:

wherein:

-   -   d. said primary gear is arranged to rotate according to a first        velocity profile;    -   e. said arm is arranged to rotate according to a second velocity        profile; and    -   f. said first and second velocity profiles are such that:        -   i. said planet gear rotates to cause said member to protrude            from the surface of the cylinder at first selected times            when the cylinder is in a given angular position; and        -   ii. said planet gear does not rotate to cause said member to            protrude from the surface of the cylinder at second selected            times when the cylinder is in said given angular position.

Such an intermittent drive system may optionally include any of thefurther features described or illustrated herein.

For a better understanding of the invention, and to show how embodimentsof the same may be carried into effect, reference will now be made, byway of example, to the accompanying diagrammatic drawings, in which:

FIG. 1 illustrates a cutting and folding station in a printing press;

FIG. 2 illustrates a conventional tucking blade drive arrangement;

FIG. 3 is a view similar to that of FIG. 2, but illustrating an improvedtucking blade drive arrangement; and

FIG. 4 is another view similar to that of FIG. 2, but illustratinganother improved tucking blade drive arrangement

FIG. 5 is another view similar to that of FIGS. 2 and 3, butillustrating an alternative embodiment.

In the figures, like references denote like or corresponding parts.

In FIG. 1, a web 1 of printed newsprint is fed to a nip between afolding cylinder 2 and a cutting cylinder 3. The folding cylinder 2carries a row of needles (not shown, but well known to the skilledreader) and the cutting cylinder 3 is provided with a serrated knife(not shown, but equally well known to the skilled reader).

The leading edge of the web 1 is impaled on the row of needles carriedon the folding cylinder 2, a small distance (e.g. 15 mm) back from whatwill be the cut. At about the same time as the needles pierce the paper,the serrated knife mounted across the cutting cylinder 3 severs the web1, leaving the leading edge of the web impaled on the needles, ready tobe carried around by the rotating folding cylinder 2.

Mounted above and close to the top of the folding cylinder 2 is a pairof folding rollers 4 providing a nip into which cut sheets carried onthe folding cylinder 2 are inserted, to make a fold. The aforementionedtucking blade is usually retained below the outer surface of thecylinder 2. However, by way of a gearing mechanism, the tucking blade isarranged to project above the surface of the cylinder 2 as it approachesthe folding rollers 4, thereby to engage the sheet of cut paper on thesurface of the cylinder 2 and push it into the nip of the foldingrollers 4, which then transport the paper upwardly as shown at 5 andthereby complete the fold.

This general mode of operation, as explained thus far, may be common toboth conventional folding and cutting stations and to embodiments of thepresent invention.

In a conventional system, with traditional printing presses, instead ofa single web 1, a plurality of identical webs are fed into the nip ofthe folding and cutting cylinders 2, 3 in suitable phase relationship,to make up a complete newspaper. The layered sheets of paper are cuttogether on the cutting cylinder 3 and travel around the foldingcylinder 2, on which they are impaled by the aforementioned needles,until the tucking blade operates adjacent the nip of the folding rollers4, to fold all of the sheets together and feed the folded sheetstogether upwardly as shown at 5.

As a point of detail, the folding rollers 4 would typically be foundbelow the folding cylinder 2 in a conventional arrangement. However, inpreferred embodiments of the present invention, they are provided at thetop of the folding cylinder 2, as other operations, not common to normalnewspaper production, are required.

FIG. 2 illustrates in further detail the tucking blade 6 of aconventional system. In the example of FIG. 2, two complementary tuckingblades 6 are provided at diametrically opposite positions with respectto the folding cylinder 2. In FIG. 2, the folding cylinder 2 isrepresented by its external diameter. A stationary ring gear 7 isdisposed coaxially around the folding cylinder 2.

A planet carrier having diametrically opposite arms 8 is mounted infixed relation to the folding cylinder 2 and is arranged to rotatecoaxially with it. Each arm 8 carries at its end a respective planetgear 9, which meshes with internal teeth of the ring gear 7 and isarranged to rotate freely on the arm 8.

Each tucking blade 6 is fixed in relation to a respective planet gear 9,such that it rotates with it. The resulting locus of travel of each ofthe tucking blades 6 is shown at 10. It can be seen from this that eachtucking blade 6 protrudes from the surface of the folding cylinder 2 atthree equally-spaced) (120°)angular positions of the rotating cylinder.

With a general configuration as illustrated in FIG. 1, when each tuckingblade 6 protrudes from the surface of the folding cylinder 2 at theuppermost angular position of the rotating cylinder, it pushes the cutsheets of paper on the surface of the cylinder 2 into the nip of thefolding rollers 4. In a conventional arrangement, the cut sheets arepresent on only about half of the cylinder surface, such that thetucking blades 6 do not engage the cut sheets in the two lower (as seenin FIG. 2) positions where they protrude from the cylinder 2.

The conventional arrangement as illustrated and described with referenceto FIGS. 1 and 2 works very well with traditional printing presses. Thegeared configuration assures reliable, high-speed operation, insynchronisation with the rest of the printing press. The provision oftwo tucking blades 6 facilitates a high throughput rate. Each of the twotucking blades 6 co-operates in turn with the folding rollers 4, duringeach revolution of the cylinder 2.

However, as described above, this arrangement becomes unsuitable whenthe web 1 that is fed to the folding and cutting cylinders 2, 3 isprovided from a digital printing press. In this case, the foldingcylinder 2 needs to perform several revolutions, during each of which asuccessive sheet of the web 1 is cut and collated on the foldingcylinder 2 with the other sheets necessary to make up the respectivepublication, prior to initiating a folding operation. Thus, the tuckingblades 6 need to be kept below the surface of the folding cylinder 2until they are required to be activated, once every x revolutions, wherex is an integer equal to 2 or more.

After considerable thought, we have come up with a modification of theconfiguration shown in FIG. 2, to provide a relatively simple andreliable means of activating tucking blades 6 intermittently.

Such an arrangement is shown in FIG. 3, where corresponding parts carrythe same references as in FIG. 2.

The principle difference between the arrangements of FIGS. 2 and 3 isthat, in FIG. 3, the ring gear 7 is not stationary but driven inrotation by a motor 11 under the control of a controller 12.

The controller 12 controls operation of the motor 11 such that, for mostof the time, the ring gear 7 rotates at the same speed as the cylinder 2and arms 8. However, when it is desired to initiate a folding operation,the ring gear 7 is momentarily stopped or slowed. The relative motionthat then occurs between the ring gear 7 and the planet gears 9 causesthe planet gears 9 to rotate about their axes and cause the respectivetucking blades 6 to protrude above the surface of the folding cylinder2, where they can engage the collated sheets on the cylinder surface andpush them into the nip of the folding rollers 4. Upon completion of themovement of the planet gears 9 and associated tucking blades 6, the ringgear 7 is again caused to move at the same angular speed as the arms 8,such that the tucking blades 6 retain their “silenced” positions, belowthe surface of the cylinder 2.

It will be appreciated that, by modern motor control techniques, themovement of the ring gear 7 can be controlled very precisely, and it maybe given any desired velocity profile. Preferably, the ring gear isservo driven. Synchronisation of the ring gear 7 with the planet arms 8and cylinder 10 may be effected in many suitable ways—for example, thering gear 7 and folding cylinder 2 may be optically coded to facilitatesynchronisation.

One possible locus of a tucking blade 6 is shown in FIG. 3 by thereference 10. As will be understood from the above, any other suitablelocus may be obtained, with a view to providing rapid and reliableoperation of the tucking blade 6 with a motion that is as smooth andgentle as possible.

It is of course necessary to activate the retaining needles on thefolding cylinder 2, in synchronism with a folding operation.Conveniently, the needles may be driven by cam operated from the shaftsof the planet gears 9, to cause the needles to retract at theappropriate time to enable a folding operation to take place, andsubsequently to project again from the cylinder surface.

FIG. 4 shows an arrangement which is similar to that of FIG. 3, but inwhich the driven ring gear 7 is replaced by a driven sun gear 17. InFIG. 4, the sun gear 7 is driven by the motor 11 under control of thecontroller 12, so as to have a velocity profile that gives rise to alocus 10 of the tucking blades 6 that is similar to that shown in FIG.3. As will be understood from the foregoing description, any otherdesired locus may be achieved by appropriate control of the motor 11. Aparticular advantage of the arrangement shown in FIG. 4 is that, becausethe sun gear 17 is much smaller than the ring gear 7, the overallinertia of the system driven by the motor 11 can be very significantlyless, thereby facilitating smooth and accurate control of the respectivevelocity profile.

In FIG. 4, there is also shown a further motor 13 that drives both theplanet carrier arms 8 and the folding cylinder 2 in rotation, undercontrol of the controller 12. If desired, the cylinder 2 may be drivenby a further motor under separate control, such that the velocityprofiles of the outputs of the respective motors and the systems thatthey drive can all be controlled independently, in line with thevelocity profile of the digital printing press.

In FIG. 4, the sun gear 17 is shown as being in direct engagement withthe planetary gears 9. However, it is possible for the sun (or ring) andplanet gears to be in driving engagement via intermediate gears which,for the purposes of this specification, includes toothed ortooth-engaging driving belts, and in the context of this specification,the term “driving engagement” is to be construed accordingly.

FIG. 5 shows an alternative arrangement in which a centre sprocket orpulley 27 is driven with a desired velocity profile by a variable speedmotor (servo motor) and is equivalent to the sun wheel 17 in FIG. 4. Thecentre sprocket or pulley 27 drives a pair of circumferentially mountedsprockets or pulleys 29 to which it is connected by one or more chain orbelt 31. The sprockets or pulleys 29 are equivalent to the planet gears9 in the previous embodiments. This arrangement results in a lowerrotary inertia as compared to either the ring gear or the sun geararrangements as previously described. Tensioning devices 32 keep the oreach chain or belt 31 under suitable tension. The general mode ofoperation of the embodiment of FIG. 5 may be readily understood from thedescription of the previous embodiments.

The tucking blades 6 in FIG. 5 may now be coupled to the motion of thecylinder 2 only through electronic control. If this coupling orsynchronisation were to fail whilst the machine is running, then it ispossible that a tucking blade 6 may start to emerge from the cylinder 2.For most of the revolution of the cylinder 2, a guard cage 33 mountedaround the circumference of the collecting cylinder 2 and its collatednewspaper sheets would restrain the tucking blade 6 whilst the cylinder2 decelerates to a stop. In this respect, it will be appreciated thatthe collated newspaper sheets would be forced into the gap betweencylinder 2 and cage 33 and act as a very effective friction brake. Theonly time this would not happen is if the tucking blade 6 starts toemerge in the vicinity of the folding rolls.

To overcome this potential problem, a cam-track device 34 is provided ateither the folding tucking blade position in the vicinity of the foldingrolls or, as shown in FIG. 5, in the vicinity of another non-foldingtucking blade 6 whilst the folding blade 6 is in the vicinity of thefolding rolls. This latter arrangement is useful where there is lessroom available in the vicinity of the folding rolls. The cam-trackdevice 34 provides two cam-tracks 36 and 37 along which travel camfollowers 35 that are attached to and rotate with each of the sprocketor pulleys 29. The cam-track 36 prevents the tucking blade 6 fromemerging if it hasn't already started to do whilst, if the blade 6 hasstarted to emerge, then the cam-track 37 forces it to emerge correctly,even if it is not driven properly by the servo motor via sprocket orpulley 27. With the cam-track device placed to guide one of thenon-folding tucking blade mechanisms, the chain or belt drive mechanismis used to force the folding tucking blade 6 to move correspondingly.

Although tucking blades 6 are shown in the illustrated embodiments asbeing driven together, any number of tucking blades can alternatively bedriven individually.

The arrangement of FIG. 3 may optionally include an idling sun gear andthat of FIG. 4 may optionally include an idling ring gear.

Although the intermittent drive mechanisms illustrated and describedabove are shown as controlling movement of tucking blades 6, they may beadapted or modified to drive other members in an intermittent manner.For example, they may control intermittent movement of cutting blades ornumbering heads (devices arranged to print consecutive numbers onconsecutive prints).

Intermittent drive mechanisms that are the subject of the presentinvention may be employed in alternative ways—e.g. for bending orforming wire in the wire forming industry. Although the illustrated useis with a paper web 1, folding, cutting or other operations may beperformed on webs of other materials, such as cloth, wood and metals.Due to the high degree of control afforded by the intermittent drivemechanisms, webs of material may be cut either into set lengths ordiffering lengths.

In this specification, the verb “comprise” has its normal dictionarymeaning, to denote non-exclusive inclusion. That is, use of the word“comprise” (or any of its derivatives) to include one feature or more,does not exclude the possibility of also including further features.

The reader's attention is directed to all and any priority documentsidentified in connection with this application and to all and any papersand documents which are filed concurrently with or previous to thisspecification in connection with this application and which are open topublic inspection with this specification, and the contents of all suchpapers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings), may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1. A sheet handling system comprising: a. a cylinder arranged to engagea sheet on the outer circumferential surface of the cylinder and totransport the sheet from an entry position to an exit position byrotation of the cylinder about its axis; and b. a drive mechanismmounted at least partly within the cylinder and arranged to cause amember to protrude intermittently from the surface of the cylinder toengage a sheet on that surface: c. said drive mechanism comprising: i. aprimary gear mounted for rotation about an axis parallel to the cylinderaxis; ii. an arm extending radially of the cylinder and mounted forrotation about an axis parallel to the cylinder axis; and iii. a planetgear mounted for rotation on said arm, in driving engagement with saidprimary gear, and operatively connected to said member: wherein: d. saidprimary gear is arranged to rotate according to a first velocityprofile; e. said arm is arranged to rotate according to a secondvelocity profile; and f. said first and second velocity profiles aresuch that: i. said planet gear rotates to cause said member to protrudefrom the surface of the cylinder at first selected times when thecylinder is in a given angular position; and ii. said planet gear doesnot rotate to cause said member to protrude from the surface of thecylinder at second selected times when the cylinder is in said givenangular position.
 2. A sheet handling system according to claim 1,wherein said primary gear is mounted for rotation about the cylinderaxis.
 3. A sheet handling system according to claim 1, wherein said armis mounted for rotation about the cylinder axis.
 4. A sheet handlingsystem according to claim 1, wherein said member is a tucking blade thatcooperates with a folding nip to fold said sheet.
 5. A sheet handlingsystem according to claim 1, wherein said member is a cutting blade. 6.A sheet handling system according to claim 1, wherein said member is anumbering head.
 7. A sheet handling system according to claim 1, whereinsaid primary gear is a sun gear.
 8. A sheet handling system according toclaim 1, wherein said primary gear is a ring gear.
 9. A sheet handlingsystem according to claim 1, further comprising a motor arranged todrive said primary gear in rotation.
 10. A sheet handling systemaccording to claim 1, further comprising a motor arranged to drive saidarm in rotation.
 11. A sheet handling system according to claim 1,wherein said arm is fixed relative to the cylinder such that the armrotates with the cylinder.
 12. A sheet handling system according toclaim 1, wherein said primary gear is fixed relative to the cylindersuch that the arm rotates with the cylinder.
 13. A sheet handling systemaccording to claim 1, further comprising control means arranged todetermine said first and/or second velocity profile.
 14. A sheethandling system according to claim 13, wherein said control means isarranged to control movement of at least one electric motor arranged todrive said primary gear and/or arm and/or cylinder in rotation.
 15. Asheet handling system according to claim 1, further comprising retainingmeans arranged to retain one or more sheet on the cylinder.
 16. A sheethandling system according to claim 15, further comprising means arrangedto engage and release said retaining means at times fixed in relation tooperation of said member.
 17. A sheet handling system according to claim1, further comprising cutting means arranged to cut a web of materialinto sheets as it is fed onto the cylinder.
 18. A sheet handling systemaccording to claim 1, comprising a plurality of planet gears mounted forrotation on respective arms of a planet carrier and in drivingengagement with said primary gear:
 19. A sheet handling system accordingto claim 1, comprising a plurality of members arranged to protrudeintermittently from the surface of the cylinder to engage a sheet onthat surface.
 20. A sheet handling system according to claims 18,wherein each said planet gear is operatively connected to a respectiveone of said members.
 21. A sheet handling system according to claim 1,further comprising guide means arranged to constrain movement of saidplanet gear when said cylinder is in said given angular position.
 22. Asheet handling system according to claim 21, wherein said guide means issuch as to constrain movement such that said planet gear may occupy onlytwo possible angular positions when said cylinder is in said givenangular position.
 23. (canceled)
 24. A printing press incorporating asheet handling system according to claim 1, arranged to cut and/orcollate and/or fold printed sheets of newsprint.
 25. A printing pressaccording to claim 24, arranged to feed a single web of printednewsprint onto the cylinder, where the web is cut, collated and folded.26. A printing press according to claim 25, wherein printing is effectedby a digital process.
 27. (canceled)
 28. (canceled)
 29. (canceled) 30.An intermittent drive system comprising: a. a cylinder mounted forrotation about its axis; and b. a drive mechanism mounted at leastpartly within the cylinder and arranged to cause a member to protrudeintermittently from the surface of the cylinder: c. said drive mechanismcomprising: i. a primary gear mounted for rotation about an axisparallel to the cylinder axis; ii. an arm extending radially of thecylinder and mounted for rotation about an axis parallel to the cylinderaxis; and iii. a planet gear mounted for rotation on said arm, indriving engagement with said primary gear, and operatively connected tosaid member: wherein: d. said primary gear is arranged to rotateaccording to a first velocity profile; e. said arm is arranged to rotateaccording to a second velocity profile; and f. said first and secondvelocity profiles are such that: i. said planet gear rotates to causesaid member to protrude from the surface of the cylinder at firstselected times when the cylinder is in a given angular position; and ii.said planet gear does not rotate to cause said member to protrude fromthe surface of the cylinder at second selected times when the cylinderis in said given angular position.
 31. (canceled)
 32. (canceled)